TL;DR

New laptop, setting up mintty configuration identical to working desktop 
system.  When connected to one specific Debian 11 (Bullseye) system (to 
which I connect often from the desktop with no issues), backspace 
appears to send ^H, and Debian interprets ^H correctly, but the terminal 
display echoes a space character instead of backing up one space.

Details

I have mintty set to term type "mintty" and "Keys/Backarrow sends ^H".

A little experimentation shows that the Debian system is correctly 
interpreting the backspace, only the mintty display is incorrect.  I 
guess there are two possibilities:

* Debian is echoing a blank when receiving ^H
* mintty is not correctly displaying the ^H echoed by Debian

Note, a local mintty session is NOT affected, backspace works fine there.

Also note when I ssh to a Debian 12 system and an old CentOS 7 system I 
don't see this issue, and when connecting from my desktop all three 
systems work.  I am stumped for how to troubleshoot this further.

I diffed the output of "stty -a" between the non-working system and one 
that works. The only differences are:

Working system: eol = <undef>; eol2 = <undef>;

Non-working system: eol = M-^?; eol2 = M-^?;

cygcheck.out attached


On the Debian 11 (non-working) system:

jhg@smtp ~
$ echo $TERM
mintty

jhg@smtp ~
$ stty -a
speed 38400 baud; rows 37; columns 128; line = 0;
intr = ^C; quit = ^\; erase = ^H; kill = ^U; eof = ^D; eol = M-^?; eol2 
= M-^?; swtch = <undef>; start = ^Q; stop = ^S;
susp = ^Z; rprnt = ^R; werase = ^W; lnext = ^V; discard = ^O; min = 1; 
time = 0;
-parenb -parodd -cmspar cs8 -hupcl -cstopb cread -clocal -crtscts
-ignbrk -brkint -ignpar -parmrk -inpck -istrip -inlcr -igncr icrnl ixon 
-ixoff -iuclc ixany imaxbel iutf8
opost -olcuc -ocrnl onlcr -onocr -onlret -ofill -ofdel nl0 cr0 tab0 bs0 
vt0 ff0
isig icanon iexten echo echoe echok -echonl -noflsh -xcase -tostop 
-echoprt echoctl echoke -flusho -extproc